Research On Urban Expansion And Driving Factors Of Hunan Province Based On DMSP/OLS Night Light Data

With the rapid development of the national economy,the urbanization process of China has rapidly increased in number and scale,and urban space is spreading and growing.Urban sprawl also poses some problems.The study and analysis of urban built-up areas and their de-evolutionary characteristics using existing technologies can provide a reference for rational urban development layout.Remote sensing technology has the characteristics of time series,wide monitoring range and high accuracy.It can effectively extract the area of urban built-up area at the regional scale in the field of urban research.At present,the research is mainly focused on the cities in the eastern developed urban agglomerations,coastal urban belts,and border cities,and there is relatively little research on central provinces in China.Since the launch of the Central Rising Strategy,the provinces of central China have been in a stage of rapid development in recent years.This article takes Hunan Province as the research object,Based on DMSP/OLS night lighting data combined with statistical data,the threshold dichotomy method has been used to extract information on the built-up areas of 14 prefecture-level cities in Hunan Province in 1995,2000,2005,2010 and 2013.To describe the expansion characteristics of 14 cities in Hunan Province in terms of the scale,structure and morphology of the city,and the main drivers of urban development in the province are also explored using various supporting data.The main elements and conclusions of the study are as follows:(1)Sensor calibration and de-saturation correction are performed on the 34-phase DMSP/OLS data from the study area using the pseudo-invariant target method to make the corrected time series images comparable.On this basis,the spatial extent of the built-up areas of 14 prefecture-level cities in Hunan Province in 1995,2000,2005,2010 and 2013 has been extracted using the threshold dichotomy method combined with statistical data.The average extraction error for each city is 3.14 percent,with a minimum extraction error of 0.1 percent and a maximum extraction error of 9 percent.The spatial location of the built-up areas extracted over the years basically coincides with the actual location of the city,and the results of this paper can be applied to urban sprawl development research.(2)Based on the extraction results of DMSP/OLS data,we analyze the temporal scale,spatial and morphological characteristics of urban built-up areas in HunanProvince in the past 20 years.In terms of dynamic changes in the scale of urban expansion,the area of urban built-up areas in Hunan Province in various periods of time,the overall growth trend,the area of the built-up area of the study area in 2013 is 2.32 times that of 1995.The difference in the distance between cities' centers has been decreasing over time,and by 2010,the distance between 14 cities' centers was almost equal,with the overall direction of center migration being first north and then south.The 14 urban built-up areas in the study area are all dominated by multi-directional sprawl,with some urban sprawl having a clear dominant direction.In terms of structural characteristics,the Gini coefficient pairs in the cities of the study area have a stable distribution of around 0.17 between 1995 and 2010,indicating that the internal structure of the cities has not changed significantly during this period.After 2010,the Gini coefficient showed an upward trend.The overall distribution of the urban rank order size coefficient?q?values ranged from 0.6 to 0.8,indicating that small and mediumsized cities are relatively well developed,large cities are underdeveloped and the urban aggregation effect is not obvious.In terms of morphological characteristics,the compactness of the cities in the study area generally shows a decreasing trend,and the compactness of the cities varies in different time periods;the city typology dimension is close to 1,and the cities as a whole show a simple rule pattern.(3)The drivers of urban development in the study area are explored using a variety of supporting information.The expansion of urban built-up areas in Hunan Province is mainly concentrated in the plains at lower altitudes with less undulating terrain,followed by the hills,where the mountainous terrain limits the expansion of urban builtup areas.The fastest growing urban economies are mostly located along important transport routes,and there is a strong correlation between urban development and total road miles.At the same time,urban development and expansion are closely linked to population and economic development.Regional development strategies and town development plans are oriented towards urban expansion.